EP1166547A1 - Codage invisible de meta-informations - Google Patents

Codage invisible de meta-informations

Info

Publication number
EP1166547A1
EP1166547A1 EP00985249A EP00985249A EP1166547A1 EP 1166547 A1 EP1166547 A1 EP 1166547A1 EP 00985249 A EP00985249 A EP 00985249A EP 00985249 A EP00985249 A EP 00985249A EP 1166547 A1 EP1166547 A1 EP 1166547A1
Authority
EP
European Patent Office
Prior art keywords
meta
information
document
content
invisible
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00985249A
Other languages
German (de)
English (en)
Inventor
Keith Ahern
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Publication of EP1166547A1 publication Critical patent/EP1166547A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F40/00—Handling natural language data
    • G06F40/10—Text processing
    • G06F40/12—Use of codes for handling textual entities
    • G06F40/163—Handling of whitespace
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F40/00—Handling natural language data
    • G06F40/10—Text processing
    • G06F40/12—Use of codes for handling textual entities
    • G06F40/123—Storage facilities
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T1/00—General purpose image data processing
    • G06T1/0021—Image watermarking
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
    • H04N1/32101—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
    • H04N1/32128—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title attached to the image data, e.g. file header, transmitted message header, information on the same page or in the same computer file as the image
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N1/00—Scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission; Details thereof
    • H04N1/32—Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device
    • H04N1/32101—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title
    • H04N1/32144—Display, printing, storage or transmission of additional information, e.g. ID code, date and time or title embedded in the image data, i.e. enclosed or integrated in the image, e.g. watermark, super-imposed logo or stamp
    • H04N1/32149—Methods relating to embedding, encoding, decoding, detection or retrieval operations
    • H04N1/32203—Spatial or amplitude domain methods
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2201/00—General purpose image data processing
    • G06T2201/005—Image watermarking
    • G06T2201/0062—Embedding of the watermark in text images, e.g. watermarking text documents using letter skew, letter distance or row distance

Definitions

  • This invention relates to the field of communications, and in particular to the encoding of meta-information, such as a digital watermark, that is related to electronic content material.
  • a watermark is traditionally used as a form of verification of the source of a document.
  • the paper used by a particular agency for currency and other negotiable instruments typically contains a watermark that is difficult to forge; a lack of the watermark is a clear indication that the instrument was not issued by that particular agency.
  • Some watermarks are also used to verify the content of the document, for example via the use of different watermarks for each denomination of currency.
  • the watermark is visually unobtrusive.
  • a digital watermark is used to verify the source, or originator, of electronically encoded content material, such as a text document.
  • the term document is used herein to identify the content material to which the digital watermark is applied.
  • the digital watermark is also used to verify that the document has not been altered since the time that it was encoded by the originator. That is, the digital watermark typically comprises both a digital signature, identifying the originator, and a content verifier, although it may only contain one or the other.
  • a digital watermark is an example of meta-information that is associated with content material.
  • meta-information include, for example, a summary or abstract of the content material, an index into the content material, an identifying label or tag for identification and use by another program, such as an HTML identification tag, and so on.
  • the digital watermark is used herein as a paradigm for meta-information that is intended to be attached to the content material in a non-intrusive fashion.
  • a variety of techniques are available for creating a digital watermark.
  • a common technique for verifying both the originator and the content of a document is to have the originator encrypt the document using a private key of a public-private key pair, the document being decrypted by the public key corresponding to this public-private key pair.
  • the public key is known publicly, and available to any or all recipients of the document, while only the originator knows the private key. Because only the originator knows the private key, only the originator could have encrypted a document that is decryptable by the originator's public key.
  • anyone having the user's public key can decrypt the document.
  • the recipient will not be able to re-encrypt the modified document such that it can be decrypted by the originator's public key, because only the originator has the private key to effect such a re-encryption. Thus, the originator cannot deny sending the document, nor claim that the document has been altered.
  • Fig. 1 illustrates an example block diagram of a prior art watermark generator
  • the watermark generator 110 includes a processor 130 that determines a parameter 131 that is associated with a document 150, such as its length or checksum, and an encrypter 140 that encrypts the parameter 131 into a watermark 111, based on a private key 141A that is known only to the originator of the document 150. Using this watermark generator 110, the encryption verifies that the originator sent the document 150 having this particular length or checksum parameter 131. If the received document (not shown) has a different length or checksum, it must be an altered version of the document 150 that was sent by the originator.
  • the receipt of a document having the appropriate length or checksum does not necessarily verify the document content, because a recipient of the original document can create an altered document having the same length or checksum, such as one that has transposed digits.
  • the receipt of an encrypted length or checksum does not necessarily verify the originator of the document, because this watermark may merely be a copy of a watermark from another document from the originator having the same length or checksum.
  • the inclusion of a length or checksum is often used for a cursory content verification, similar to the numbering of pages in a printed document, wherein a missing page is evident.
  • an encrypted length or checksum is also often used for a cursory originator verification, similar to a person's signature, which may be forged, on a printed document.
  • An alternative to ai inclusion of a length or checksum of a document is the inclusion of a "hash value" of the document as the parameter 131.
  • the recipient Upon receipt, the recipient applies the same hashing function to the document without the included hash value parameter 131, and compares the resultant hash value to a decryption of the watermark 111 that is included with the document.
  • a preferred hashing function is one that is not easily reversible and not easily determinable.
  • a hash value parameter 131 of the document 150 provides an effective verification of content.
  • the subsequent encryption of the hash value parameter 131 using the originator's private key 141A provides an effective verification of the originator, because a prior document is highly unlikely to have the same hash value parameter 131.
  • meta-information is included within a separate section of the communicated document, using for example, a MLME, a HTML, or other encoding standard.
  • a "tag" that identifies the start of the section, and a corresponding tag that identifies the end of the section serve to identify each section of the document, in this example, the content material and each meta-information item.
  • a receiving application that is compatible with the encoding standard segregates the document and processes each section accordingly.
  • the material between a "Begin Text” tag and an "End Text” tag in a document will be displayed on a display device; the material between a "Begin Watermark” tag and an “End Watermark” tag will be processed to verify either the content or the originator, or both, and a corresponding document, such as "This document is verified as having been communicated from Alice" will also be displayed, or rendered as a vocal message.
  • a device that is not compatible with the particular standard will not recognize the segmentation tags, and will typically display the document, with the included meta-information and the aforementioned tags, on a display device.
  • the text will, in general, be recognizable, the inclusion of a display of the meta-information and tags is visually unappealing.
  • an ideal meta- information item in an electronic document is one that is visually unobtrusive. It is an object of this invention to provide a means for including a substantially “invisible” digital watermark, or other meta-information, within an electronic document. It is a further object of this invention to provide a means for encoding meta-information into an "invisible” form.
  • meta-information such as a digital watermark
  • characters that are not visually apparent when the document is rendered, and attaching this encoded meta-information to the document.
  • Characters such as spaces, tabs, carriage returns, backspaces, line feeds, and so on are used to encode the meta- information.
  • a receiving device that is compatible with this encoding is able to decode and process the meta-information; for example, to decode a watermark and verify the contents and/or the originator of the document.
  • a receiving device that is not compatible with this encoding will merely display or print additional "white space".
  • this additional white space will occur after the display or printing of the document, in a visually unobtrusive form.
  • Fig. 1 illustrates an example block diagram of a prior art watermark generator.
  • Fig. 2 illustrates an example block diagram of an encoder in accordance with this invention, using a watermark as the example meta-information.
  • Figs. 3A and 3B illustrate example invisible encodings of a binary digit in accordance with this invention.
  • Fig. 4 illustrates an example flow diagram of an invisible watermark encoder in accordance with this invention.
  • Fig. 5 illustrates an example block diagram of an invisible watermark decoder in accordance with this invention.
  • Fig. 2 illustrates an example block diagram of an encoder 200 in accordance with this invention.
  • the example encoder 200 includes an example meta-information generator and an invisible encoder 220.
  • the example watermark generator 110 of Fig. 1 is used as a representation of a typical meta-information generator.
  • the watermark generator 110 of Fig. 1 contains both a content verification processor 130 and an encrypter 140, although some conventional watermark generators may have only one or the other, or may be configured differently than shown.
  • the particular embodiment of the meta-information generator 110 is immaterial to the principles presented in this specification.
  • the invention is presented in terms of a digital watermark as a paradigm for meta- information, in general.
  • the watermark generator 110 provides a watermark 111 that is associated with the content 250A of the document 250, as discussed above with respect to Fig. 1.
  • the invisible encoder 220 encodes the watermark 111 as a group of characters that are invisible when rendered to create an invisible watermark 221.
  • Figs. 3 A and 3B illustrate example invisible encodings of a binary digit 311 in accordance with this invention.
  • the binary digit 311 for example, represents a single byte of the digital watermark 111 that has a binary value of "01100100".
  • a "space" character (Sp) is used to represent a bit value of "0”
  • a "carriage return” character (CR) is used to represent a bit value of "1”
  • the encoding of the binary value "01100100” 311 is "Sp-CR-CR-Sp-Sp-CR-Sp-Sp" 321.
  • Fig. 3B illustrates an alternative encoding of the same binary value "01100100” using four possible “invisible” characters: "space” (Sp), “line feed” (LF), “tab” (Tb), and “carriage return” (CR), corresponding to binary pairs “00", "01", “10 ', and "11” respectively.
  • the binary value "01100100” 311 is "LF-Tb-LF-Sp" (01-10-01- 00) 321'.
  • an alternative invisible encoding using the principles presented in the referenced copending application is the use of the "backspace" character to erase, and therefore render invisible, sequences of visible characters.
  • the invisible watermark 221 is these sixty (visible) characters followed by, or interspersed with, sixty "backspace" characters that have the effect of erasing the visible characters from a display.
  • the invisible watermark 221 is appended to the content 250A of the document 250, as illustrated by segment 250B or the document 250 in Fig. 2.
  • the term “appended” is used herein in its most general sense of "added to”, the particular method used to add, merge, attach, bind, etc. the invisible watermark 221 is irrelevant to this invention.
  • the invisible watermark 221 is appended to the end of the document, for ease of identification and processing, as well as to allow for the content material to be processed and presented before the watermark processing.
  • the invisible watermark 221 includes a delineator, also invisibly encoded, that marks the beginning of the invisible watermark 221.
  • the delineator is a predetermined encoding that is highly unlikely, preferably never, to appear within the content 250A of any document 250. For example, if spaces (S) and tabs (T) are used to invisibly encode the watermark, a sequence of "STSSTTTSTSTST", or other seemingly random assortment of invisible characters, may be used to delineate the start of the invisible watermark 221. Alternatively, the last invisible sequence in the invisible watermark 221 may contain an indication of the length of the invisible watermark 221, from which the decoder can determine the beginning of the invisible watermark 221, thereby eliminating the need for a unique delineator. These and other methods of distinguishing segments of a document are common in the art. Note that the invisible encoding need not be contiguous; for example, the invisible encoding may be placed in each corner of a document, in the margins, in the space between paragraphs, and so on.
  • the resultant document 250 comprising the document content 250A and an invisibly encoded watermark 250B is thereafter communicated 261 to receiving devices (not shown) via a transmitter 260.
  • receiving devices not shown
  • a recipient of the document 250 will be able to view the content 250A of the document without any visually disturbing artifacts associated with the inclusion of a watermark, regardless of whether the receiving device used to receive the document 250 is capable of processing the invisibly encoded watermark.
  • a user who receives the document 250 via a non-capable receiving device will not be able to process the watermark to verify the content or the originator, but will not be encumbered in viewing the document content.
  • FIG. 4 illustrates an example flow diagram of an invisible watermark encoder in accordance with this invention, such as might be used in the encoder 200 of Fig. 2.
  • the document is received by the encoder, and at 420, a content verification parameter is determined, based on the content of the document.
  • the content verification parameter is a length, a checksum, a hash value, or other parameter corresponding to the document that can be also determined by a receiver of the document, for comparison with this parameter.
  • the content verification parameter is encrypted, at 430, preferably via a private key of a public- private key pair that is only known to the originator, or signer, of the document.
  • the encrypted content verification parameter forms the watermark, and is encoded as a group of characters that are invisible when rendered, at 440, using any one of a variety of invisible encoding techniques, as discussed above with respect to Fig. 2. Note that the selected invisible encoding technique must also be known to the recipient of the document in order to utilize the invisibly encoded watermark for verification purposes.
  • the invisible sequence corresponding to the watermark is attached to the document, at 450, and the resultant document, with attached invisible watermark, is transmitted to one or more recipients, at 460.
  • the transmission at 460 may be, for example, a transmission of the document via the Internet, a point-to-point transmission to a particular recipient, a file transfer via a local area network, and so on.
  • Fig. 5 illustrates an example block diagram of an invisible watermark decoder 500 in accordance with this invention.
  • a receiver 510 receives the transmitted document 261 (of FIG. 2) that comprises content material 250A and an invisibly encoded verification sequence 250B.
  • a parser 520 segregates the received document 261 into these segments 250A, 250B. The parser 520 effects the segregation based on the techniques used to delineate the segments 250A, 250B, as discussed above with respect to Fig. 2.
  • the content material 250A is displayed directly on a display device 580.
  • the term "display device” is used generically; the device 580 may be portable or stationary, and may comprise a display monitor such as in a TV or of a PC, PDA, pager, a printer, a television, and so on, and may also include audio or other capabilities.
  • the invisible sequence decoder 530 decodes the invisible sequence 250B based on the method used to encode the watermark, as discussed above with respect to Figs. 3A, 3B, and 4, and produces a decoded watermark 531.
  • the decrypter 540 decrypts the watermark 531 using a public key 141B that corresponds to the private key 141A (Figs. 1 and 2) that was used to encrypt the content verification parameter.
  • the comparator 560 compares the decrypted content verification parameter 545 to a content parameter 555 that is produced by a content verification processor 550.
  • the content verification processor 550 performs the same function as the content verification processor 130 of Fig. 1. Therefore, if the content material 250A of Fig. 5 is identical to the content material 250A of Fig. 2, as it should be, the content parameter 555 that is produced by the content verification processor 550 is identical to the decrypted content verification parameter 545.
  • the verification notifier 570 notifies the user of the results of the comparison, optionally as a communication via the display device 580.
  • the creation of the invisible watermark may be effected within the transmitter 260, and appended to the document 250 to form the transmission 261, leaving the original document 250 unaffected.
  • a separate document 250' may be created that includes the original document 250 plus an appended invisible watermark 250B, without affecting the original document 250.
  • the principles of this invention may be combined with other invisible encoding techniques.
  • the content document 250A may contain invisible encodings that affect the appearance of the document 250A on the display device 580, using the principles presented in the aforementioned copending U.S. patent application "Invisible Encoding of Attribute Data in Character Based Documents and Files", U.S. serial number 09/333,632, filed 6/15/99 for Keith Ahern, Attorney docket PHA 23,675.
  • copending U.S. patent application "Script Embedded in Electronic Documents as Invisible Encoding", U.S. serial number , filed for Keith Ahern, Attorney docket PHA 23,778, presents the encoding of scripts via invisible encodings
  • copending U.S. patent application "Invisible Encoding For Control of Delivery" U.S. serial number 09/425,652, filed 10/22/99 for Keith Ahern, Attorney docket PHA 23,777, presents the encoding of document delivery options via invisible encodings, and are incorporated by reference herein.

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  • Engineering & Computer Science (AREA)
  • Theoretical Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • Computational Linguistics (AREA)
  • General Health & Medical Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Artificial Intelligence (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Editing Of Facsimile Originals (AREA)
  • Image Processing (AREA)
  • Storage Device Security (AREA)

Abstract

Selon l'invention, on code des méta-informations, telles qu'un filigrane numérique, associées à un document, en utilisant des caractères ou des suites de caractères, qui sont 'invisibles', lors de leur rendu. On utilise des caractères tels que des espaces, tabulations, retours de chariot, espaces arrière, changements de ligne, etc., pour coder le filigrane. De préférence, l'article de méta-informations 'invisibles' codées est attaché au document. Un dispositif récepteur, compatible avec ce codage peut décoder et traiter les méta-informations, par exemple pour vérifier le contenu et/ou l'expéditeur du document. Un dispositif récepteur qui n'est pas compatible avec ce codage va simplement afficher ou imprimer des 'espaces blancs' additionnels correspondant aux méta-informations 'invisibles'. En attachant ce codage invisible au document, cet espace blanc supplémentaire se produit après affichage ou impression du document, de manière non gênante visuellement.
EP00985249A 2000-01-19 2000-12-22 Codage invisible de meta-informations Withdrawn EP1166547A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US09/487,150 US6769061B1 (en) 2000-01-19 2000-01-19 Invisible encoding of meta-information
US487150 2000-01-19
PCT/EP2000/013198 WO2001054396A1 (fr) 2000-01-19 2000-12-22 Codage invisible de meta-informations

Publications (1)

Publication Number Publication Date
EP1166547A1 true EP1166547A1 (fr) 2002-01-02

Family

ID=23934606

Family Applications (1)

Application Number Title Priority Date Filing Date
EP00985249A Withdrawn EP1166547A1 (fr) 2000-01-19 2000-12-22 Codage invisible de meta-informations

Country Status (5)

Country Link
US (1) US6769061B1 (fr)
EP (1) EP1166547A1 (fr)
JP (1) JP2003520527A (fr)
CN (1) CN1182698C (fr)
WO (1) WO2001054396A1 (fr)

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WO2001054396A1 (fr) 2001-07-26
US6769061B1 (en) 2004-07-27

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